Cushioning-material structure for vehicle seat

ABSTRACT

The purpose of the present invention is to provide a cushioning material structure, for a vehicle seat, that makes it possible to reduce the weight of the vehicle seat while maintaining stable riding performance. A cushioning material supported by the top surface of a bottom plate provided on a vehicle body is provided with voids. This allows weight reduction without reducing the thickness of the cushioning material as in conventional cushioning-material structures, thereby making it possible to reduce the weight of the vehicle seat while maintaining stable riding performance.

The present application is a continuation application of applicationSer. No. 14/409,864 filed Dec. 19, 2014, which in turn is a U.S.national stage application of PCT/JP2013/067606 filed Jun. 27, 2013. Theentire disclosures of the prior applications are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a cushion material structure for avehicle seat, such vehicle seat including seats of two wheeled vehiclessuch as motorcycles, scooters, snow mobiles and personal watercrafts,three wheeled buggies, straddle type vehicles and seats of constructionmachines.

BACKGROUND ART

As for vehicle seats of automatic two wheeled vehicles and the like,vehicle seats made by cushion materials being placed on bottom platesand being covered with surface material are known (for example, seePatent Document 1).

The cushion material described in Patent Document 1 is a solid materialand the under surface thereof is formed in a shape that corresponds tothe shape of the upper surface of the bottom plate, the under surface ofthe cushion material being tightly in contact with the upper surface ofthe bottom plate.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Unexamined Patent Application PublicationNo. 2007-314021

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

In view of weight saving of the vehicle body, there has been a desire tomake the vehicle seat lighter. As one method, there has been an idea ofmaking the cushion material thinner, for example. However, the cushionmaterial cannot bend easily if it is made thin, and there are problemsthat the cushion material may have trouble absorbing the vibration andthe like caused by the unevenness of the roads and that the sittingcondition is not comfortable.

An object of the present invention is to provide a cushion materialstructure of a vehicle seat which realizes weight saving in a vehicleseat while maintaining stable sitting.

Means for Solving the Problem

In order to solve the above problems, the invention of an embodiment isa cushion material structure of a vehicle seat, including a cushionmaterial having a space section, wherein the cushion material issupported by an upper surface of a bottom plate which is provided on avehicle body.

The invention of an embodiment is the cushion material structure,wherein the space section is formed at a back side of the cushionmaterial and is a concave section opened toward the bottom plate.

The invention of an embodiment is the cushion material structure,wherein a plurality of concave sections are formed in the cushionmaterial, and the plurality of concave sections are arranged along awidth-wise center of the cushion material in a front-to-back directionof the cushion material.

The invention of an embodiment is the cushion material structure,wherein a plurality of mounting sections which are to be fixed to thevehicle body are arranged along an inner periphery at the back side ofthe bottom plate with spaces therebetween, and a plurality of otherconcave sections are formed in the cushion material between partscorresponding to positions of the plurality of mounting sections and theplurality of concave sections arranged along the width-wise center ofthe cushion material.

The invention of an embodiment is the cushion material structure,wherein the plurality of concave sections are arranged in a gridpattern.

The invention of an embodiment is the cushion material structure,wherein the cushion material further includes a pair of expected ischiumsections as regions in the cushion material expected to correspond to anischium position of a passenger, and the plurality of concave sectionsare arranged avoiding the pair of expected ischium sections.

The invention of an embodiment is the cushion material structure,wherein the bottom plate includes a reinforcement section which bulgesat a back side of the bottom plate and which is recessed at an upperside of the bottom plate, and a reference surface is arranged so as tovertically face the reinforcement section.

The invention of an embodiment is the cushion material structure,wherein a length of a part in the reference surface corresponding to astraight line connecting centers of concave sections which are adjacentto each other in a left-to-right direction of the vehicle seat and awidth of the reinforcement section are equal.

The invention of an embodiment is the cushion material structure,wherein a reference surface side periphery of a concave section arrangedbetween the expected ischium sections which form the pair is supportedby the bottom plate.

The invention of an embodiment is the cushion material structure,wherein concave sections are respectively arranged on the left and rightof the concave section arranged between the expected ischium sectionswhich form the pair, and only outside parts of reference surface sideperipheries of the left and right concave sections are supported by thebottom plate.

The invention of an embodiment is the cushion material structure,wherein among the plurality of concave sections, one concave section andanother concave section which is different from the one concave sectionare in communication with each other through the reinforcement sectionformed at the upper side of the bottom plate so as to be recessed.

The invention of an embodiment is the cushion material structure,wherein the cushion material is formed so as to bend at a part otherthan an upper layer part thereof.

The invention of an embodiment is the cushion material structure,wherein the cushion material is formed so as to bend at a lowest layerpart thereof.

The invention of an embodiment is the cushion material structure,wherein the bottom plate includes a main surface section and a subsurface section which is arranged in front of the main surface sectionand which is tilted upward with respect to the main surface section, andat least one space section is formed in the cushion material at a partcorresponding to a bent section between the main surface section and thesub surface section.

The invention of an embodiment is the cushion material structure,wherein wall sections which extend vertically are formed in the bottomplate so as to face each other at left and right on the bent section,the wall sections formed along the front-to-back direction.

The invention of an embodiment is the cushion material structure whereinan opening is formed in the bottom plate at a position facing thevehicle body, and a space section is formed in the cushion material at aposition facing the opening.

Advantageous Effect of the Invention

According to an embodiment, since the cushion material is provided withthe space section, the cushion material can be made lighter withoutmaking it thinner as in a conventional case. Thereby, the vehicle seatcan be made lighter while maintaining a stable sitting.

According to an embodiment, the space section is formed on the back sideof the cushion material and is a concave section opened toward thebottom plate. Therefore, the cushion material can bend toward the bottomplate easily when a passenger sits on the vehicle seat.

According to an embodiment, due to the plurality of concave sectionsarranged in a line, the width-wise center of the cushion material canbend easily in the front-to-back direction of the cushion material.

According to an embodiment, since the bottom plate is fixed to thevehicle body via the plurality of mounting sections, rigidity of thebottom plate itself can be improved. Further, since the plurality ofconcave sections can be formed in the cushion material within the rangewhere rigidity of the bottom plate is improved by the plurality ofmounting sections, the likeliness of bending in the cushion material canbe improved more while stably supporting the cushion material with thebottom plate.

According to an embodiment, the plurality of concave sections can belined neatly and efficiently within the back side range of the cushionmaterial. Thus, a great number of concave sections can be formed.

According to an embodiment, since the plurality of concave sections arearranged avoiding the pair of expected ischium sections, referencesurface is to be arranged at the positions of the pair of the expectedischium sections. Thus, the ischium position of a passenger can besupported stably.

According to an embodiment, when the cushion material is to bend, thecushion material can sink more downward than the reference surface byusing the difference in level of the reinforcement section. Thus, thecushion material can bend easily.

According to an embodiment, the part in the reference surfacecorresponding to the straight line connecting the centers of concavesections which are adjacent to each other in the left-to-right directionof the vehicle seat is prevented from sinking in the recess of thereinforcement section, and the cushion material can be prevented frompartially caving in.

According to an embodiment, the periphery of the concave section betweenthe pair of expected ischium sections where a passenger load is likelyto be applied is supported by the bottom plate. Thus, vicinity of thepair of expected ischium sections can be supported stably whilemaintaining the likeliness of bending at vicinity of the pair ofexpected ischium sections by the concave section.

According to an embodiment, by the outside parts of the referencesurface side peripheries of the left and right concaves, the positionswhere the load is likely to be applied when the vehicle enters a curvecan be supported. Thus, sitting can be stable when the vehicle enters acurve.

According to an embodiment, the air can be let out to another concavesection from one concave section through the reinforcement section whenthe cushion material bends. Thus, the cushion material can bend moreeasily.

It has been said that, in general, a passenger can sit comfortably whenhe/she can feel the hardness to a certain extent in a vehicle seat of atwo wheeled vehicle or the like. Therefore, as in an embodiment, if thecushion material is formed so as to bend at a part other than the upperlayers thereof, the cushion material is not likely to bend in the upperlayers thereof and the passenger can feel a certain level of hardness.On the other hand, since a part other than the upper layers of thecushion material is more likely to bend comparing to the upper layers,this part can absorb the vibration and the like caused by the unevennessof the road surface. Therefore, even if the cushion material is madethinner and the vehicle seat is made lighter, a stable sitting can bemaintained.

According to an embodiment, since the cushion material is formed so asto bend at the lowest layer part thereof, the cushion material bends atthe lowest layer part that is the furthest from the upper layer part.Thus, the upper layer part can be prevented from deforming with thebending of the lowest layer part and the sitting condition can beprevented from becoming uncomfortable due to bending.

In most cases, the bent section in the bottom plate between the mainsurface section and the sub surface section is where the buttocks of apassenger are to be placed. That is, if the cushioning properties atthis section is improved, a passenger can sit more comfortably. Asdescribed in an embodiment, if at least one space section is formed atthe bending part in the cushion material, the cushioning properties canbe ensured by the space section even if the cushion material is madethin. Thus, a stable sitting can be maintained.

According to an embodiment, since the wall sections which extendvertically are formed at the left and right of the bottom plate on thebent section, the wall sections being formed along the front-to-backdirection, rigidity at the bent section can be improved by the wallsections. If rigidity at the bent section in the front-to-back directionis improved, the bottom plate can be prevented from twisting, and thus,even more comfortable sitting condition can be provided.

In the bottom plate, openings through which the fixation member providedat the fuel tank of the vehicle body and the engaging section forpositioning which is provided at the rear of the vehicle body areexposed are formed. Vicinity parts of these openings are not directlyrelevant to supporting the vehicle seat. Therefore, even if spacesections are formed at the positions in the cushion material facing theopenings, stability of the vehicle seat can be maintained and a stablesitting can also be maintained. Further, by forming the space sections,the vehicle seat can also be made lighter.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of a vehicle seat according to the firstembodiment.

FIG. 2 is a cross-sectional view of the vehicle seat according to thefirst embodiment.

FIG. 3 is an enlarged cross-sectional view of a part of the vehicle seataccording to the first embodiment.

FIG. 4 is a schematic view of a bottom plate according to the firstembodiment.

FIG. 5 is a plan view of the bottom plate according to the firstembodiment.

FIG. 6 is an underside of a cushion material according to the firstembodiment.

FIG. 7 is a side cross-sectional view of the vehicle seat shown in FIG.1.

FIG. 8 is a cross-sectional view when cut along the line A-A shown inFIG. 7.

FIG. 9 is a cross-sectional view when cut along the line B-B shown inFIG. 7.

FIG. 10 is a cross-sectional view when cut along the line C-C shown inFIG. 7.

FIG. 11 is a cross-sectional view when cut along the line D-D shown inFIG. 7.

FIG. 12 is a cross-sectional view when cut along the line E-E shown inFIG. 7.

FIG. 13 is a cross-sectional view when cut along the line F-F shown inFIG. 7.

FIG. 14 is a cross-sectional view when cut along the line G-G shown inFIG. 7.

FIG. 15 is a cross-sectional view when cut along the line H-H shown inFIG. 7.

FIG. 16 is a diagram for explaining an arrangement of concave sectionsin the cushion material according to the first embodiment.

FIG. 17 is a diagram for explaining an arrangement of concave sectionsand the expected ischium position according to the first embodiment.

FIG. 18 is a diagram explaining a state where the cushion material isbent according to the first embodiment.

FIG. 19 is a side view of a vehicle seat according to the secondembodiment.

FIG. 20 is a cross-sectional view of the vehicle seat according to thesecond embodiment.

FIG. 21 is an enlarged cross-sectional view of a part of the vehicleseat according to the second embodiment.

FIG. 22 is a schematic view of a bottom plate according to the secondembodiment.

FIG. 23 is a plan view of the bottom plate according to the secondembodiment.

FIG. 24 is an underside of a cushion material according to the secondembodiment.

FIG. 25 is a side cross-sectional view of the vehicle seat shown in FIG.19.

FIG. 26 is a cross-sectional view when cut along the line A-A shown inFIG. 25.

FIG. 27 is a cross-sectional view when cut along the line B-B shown inFIG. 25.

FIG. 28 is a cross-sectional view when cut along the line C-C shown inFIG. 25.

FIG. 29 is a cross-sectional view when cut along the line D-D shown inFIG. 25.

FIG. 30 is a cross-sectional view when cut along the line E-E shown inFIG. 25.

FIG. 31 is a cross-sectional view when cut along the line F-F shown inFIG. 25.

FIG. 32 is a cross-sectional view when cut along the line G-G shown inFIG. 25.

FIG. 33 is a cross-sectional view when cut along the line H-H shown inFIG. 25.

FIG. 34 is a diagram for explaining an arrangement of concave sectionsin the cushion material according to the second embodiment.

FIG. 35 is a diagram for explaining a positional relation betweenindividual parts of the bottom plate and the concave sections accordingto the second embodiment.

FIG. 36 is a diagram for explaining a state where the cushion materialis not bent according to the second embodiment.

FIG. 37 is a diagram for explaining a state where the cushion materialis bent according to the second embodiment.

FIG. 38 is a cross-sectional view showing an overall structure near thefront side opening of the bottom plate according to the secondembodiment.

FIG. 39 is a schematic view where a part near the front side opening ofthe bottom plate according to the second embodiment is fractured.

FIG. 40 is a schematic view where a part near the rear side opening ofthe bottom plate according to the second embodiment is fractured.

FIG. 41 is a cross-sectional view showing an overall structure near therear side opening of the bottom plate according to the secondembodiment.

FIG. 42 is a side cross-sectional view showing a modification example ofthe cushion material according to the second embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

Hereinafter, the first embodiment of the present invention will bedescribed with reference to the drawings.

In FIG. 1, the reference numeral 1 indicates a vehicle seat. The vehicleseat 1 of the embodiment is to be used in an automatic two wheeledvehicle.

Here, the vehicle seat is not limited to the seats used in automatic twowheeled vehicles as in the embodiment. The vehicle seat includes seatsof two wheeled vehicles such as motorcycles, scooters, snowmobiles andpersonal watercrafts, three wheeled buggies, straddle type vehicles,seats of construction machines, four wheeled vehicles, etc.

The vehicle seat 1 includes a bottom plate 10 which is provided on avehicle body 2 of an automatic two wheeled vehicle, a cushion material20 which is supported by the upper surface of the bottom plate 10 and asurface material 3 which covers the bottom plate 10 and the cushionmaterial 20. That is, the vehicle seat 1 is formed by the cushionmaterial 20 being supported on the bottom plate 10 and the cushionmaterial 20 and the bottom plate 10 being covered with the surfacematerial 3.

The parts of the vehicle body 2 where the bottom plate 10 is to be fixedare, in particular, the seat rail 2 a which is laid on the vehicle body2 and the fuel tank 2 b in front of the vehicle seat 1.

The bottom plate 10 is formed by a resin material such as polypropylene,polyvinylchloride, etc., and is formed in a shape corresponding to theshape of the vehicle body 2 of the automatic two wheeled vehicle. Thebottom plate 10 is attached to the vehicle body 2.

The bottom plate 10 of the embodiment is formed by using polypropyleneas a material, for example. In order to fixate the bottom plate 10 tothe vehicle body 2 of the automatic two wheeled vehicle, thepolypropylene is to be especially hard. The bottom plate 10 may beprovided with clasps or the like necessary to be fixed to the vehiclebody 2 of the automatic two wheeled vehicle.

The cushion material 20 is formed of a soft foam material such as, forexample, urethane foam, polypropylene foam or polyethylene foam. As forthe cushion material 20 of the embodiment, for example, urethane foam isused.

Since the cushion material 20 is supported by the upper surface of thebottom plate 10, the under surface of the cushion material 20 is formedin a shape reflecting the shape of the upper surface of the bottom plate10. Thereby, the cushion material 20 can be supported stably by theupper surface of the bottom plate 10. The surfaces of the bottom plate10 and the cushion material 20 which contact each other, that is, theupper surface of the bottom plate 10 and the under surface of thecushion material 20 are referred to as the reference surfaces 10 a and20 a, respectively.

The cushion material 20 is formed so that the part in the upper surfacethereof where a passenger who drives the automatic two wheeled vehiclesits is lower than the other portion when seen from a side. This part isreferred to as the lowest position 1 a that is the lowest along thewidth-wise center C2 of the vehicle seat 1 in the front-to-backdirection of the vehicle seat 1. The part near the lowest position 1 acorresponds to the ischium position of the passenger who drives theautomatic two wheeled vehicle and is the maximum load section where agreat portion of the load of a passenger is applied in the vehicle seat1.

The surface material 3 constitutes the sitting surface of the vehicleseat 1. The surface material 3 is where comes in contact with apassenger and is formed by a resin material such as polypropylene,polyvinylchloride or the like. As for the surface material 3 of theembodiment, for example, a hard material made of polypropylene is used.

As shown in FIG. 3, the edge 3 a of the surface material 3 is folded into the back side of the bottom plate 10 and is fixed to the back side ofthe bottom plate 10 by staples 4.

The edge 3 a of the surface material 3 refers to the entire peripheryedge of the surface material 3. Therefore, the edge 3 a of the surfacematerial 3 is fixed along the entire periphery edge of the bottom plate10.

Next, the bottom plate 10 will be described in more detail.

The bottom plate 10 includes a plurality of reinforcement sections 11which intersect with the width-wise center C1 of the bottom plate 10, atleast a part of each reinforcement section being arranged obliquely withrespect to the front-to-back direction of the vehicle seat as an obliqueline. That is, the reinforcement sections 11 are not merely arrangedvertically or horizontally (from front to rear or from side to side) inthe bottom plate 10. By each of the reinforcement sections 11 includinga part that is arranged obliquely, it is expected to obtain rigidity inthe front-to-back direction and in the right-to-left direction.

The reinforcement sections 11 of the embodiment bulge at the back sideof the bottom plate 10 and are recessed at the upper side of the bottomplate 10. That is, as shown in FIGS. 2, 10, etc., each reinforcementsection 11 is formed in a cross-sectional concave shape and includes apair of side walls 11 b and 11 b each of which formed by being bentdownward from the upper surface of the bottom plate 10 and the bottomwhich is formed in an integrated fashion being bridged between the loweredges of the side walls 11 b and 11 b that form a pair. Corners wherethe bottom plate 10 is turned downward from the upper surface thereofare referred to as turning sections 11 a and are the parts in thereinforcement sections 11 having high rigidity.

The upper side of the bottom plate 10 includes the upper surface of thebottom plate 10 and the upper side of the step section 14 b (describedlater) which is formed along the entire periphery edge of the bottomplate 10 and which is bent toward the vehicle body 2 more than the uppersurface of the bottom plate 10. On the other hand, the back side of thebottom plate 10 is the back of the upper side of the bottom plate 10 andincludes the under surface of the bottom plate 10 and the back side ofthe step section 14 b.

According to the above described reinforcement sections 11, aconcave-convex figure is formed in the bottom plate 10 leading toimprovement in rigidity of the bottom plate 10. Further, since thebottom plate 10 can be reinforced in a state where the upper sidethereof is partially recessed, bending of the cushion material 20 whichis supported by the upper surface of the bottom late 10 is not inhibitedcomparing to a case where the bottom plate 10 is reinforced in a statewhere the upper side thereof is partially bulged. Therefore, acomfortable sitting condition can be provided to a passenger.

Although the reinforcement sections 11 are formed in a cross-sectionalconcave shape in the embodiment, this is not limitative in any way. Thereinforcement sections 11 may be formed in a protruding shape such as arib on the back side of the bottom plate 10.

As shown in FIGS. 4, 5, 7, etc., the bottom plate 10 is provided with aplurality of mounting sections 12 through which the bottom plate 10 isfixed to the vehicle body 2, the mounting sections 12 being formed onthe back side of the bottom plate 10 with spaces therebetween.

The mounting sections 12 refer to the parts which are to be fixed to thevehicle body 2 themselves and also to elastic members such as rubbersattached to the above parts and the parts where the elastic members areto be attached.

As shown in FIGS. 8, 9, 13 and 14, these elastic members have projectedinsertion sections and are fixed to the bottom plate 10 by the insertionsections being inserted to and engaged with the insertion holes formedin the bottom plate 10. Here, the elastic member may be fixed to theunderside of the bottom plate 10 by welding or the like, for example.

In each of the elastic members of the mounting sections 12, a bolt holeis formed near the center thereof. The bottom plate 10 can be fixed tothe seat rail 2 a of the vehicle body 2 by the bolts which are insertedthrough the bolt holes.

With respect to a part where the distance to the seat rail 2 a is long,a leg section 12 a is formed on the back side of the bottom plate 10 inan integrated fashion and an elastic member of a mounting section 12 isfixed at the tip of the leg section 12 a. That is, such mounting section12 includes the leg section 12 a.

The leg section 12 a is formed so as to be recessed at the upper side ofthe bottom plate 10. That is, the leg section 12 a includes a concavesection 12 b which is recessed at the upper side of the bottom plate 10.

The plurality of mounting sections 12 of the embodiment aresymmetrically arranged at eight points on the back side of the bottomplate 10. Pairs of mounting sections 12 and 12 are arranged in four rowsalong the front-to-back direction of the bottom plate 10, the mountingsections 12 and 12 forming each pair are arranged widthwise.

The mounting sections 12, 12 which are provided at the front end part ofthe bottom plate 10 (in the first row from the front) among theplurality of mounting sections 12 abut the fuel tank 2 b of the vehiclebody 2 as shown in FIG. 7. These mounting sections 12, 12 in the firstrow are not fixed to the fuel tank 2 b by bolts and are not fixed to theseat rail 2 a.

The reinforcement sections 11 are arranged between the plurality ofmounting sections 12, 12 which are apart from each other. In theembodiment, the bottom plate 10 is provided with a plurality ofreinforcement sections 11 as shown in FIGS. 4 and 5. The bottom plate 10further includes intersections 13 where the plurality of reinforcementsections 11 intersect with each other. That is, the plurality ofreinforcement sections 11 are made to intersect with each other and arearranged in different directions. Comparing to a case where theplurality of reinforcement sections 11 are not made to intersect witheach other, in the above arrangement, rigidity of the bottom plate canbe improved more.

The plurality of reinforcement sections 11 of the embodiment aresymmetrically arranged when being arranged in different directions.

Further, in the embodiment, the bottom plate 10 is provided, with aplurality of intersections 13.

On the surface of one of the plurality of intersections 13, 13, areinforcement rib 13 a for improving rigidity at the intersection 13 isformed in an integrated fashion.

The plurality of intersections 13 and 13 are arranged along thewidth-wise center C1 of the bottom plate 10 leading to improvingrigidity at the width-wise center C1 in the bottom plate 10 where theload is likely to be applied.

Further, the plurality of intersections 13 and 13 are arranged avoidingthe lowest position 1 a in the bottom plate 10. The lowest position 1 ain the bottom plate 10 is the maximum, load section where a greatportion of the load of a passenger is applied. The intersections 13 arethe parts in the bottom plate 10 where rigidity is improved. Therefore,the position where the passenger load is applied greatly and the partswhere rigidity is improved by the intersections 13 do not overlap.Thereby, the passenger can be prevented from feeling a stronguncomfortable pressure and a comfortable sitting condition can beprovided to the passenger.

In the embodiment, as shown in FIG. 5, the front side intersection 13 ofthe plurality of intersections 13 and 13 is disposed between themounting sections 12 and 12 of the second row and the mounting sections12 and 12 of the third row, the rows being counted from the front. Onthe other hand, the lowest position 1 a, which is the maximum loadsection, is between the mounting sections 12 and 12 of the first row andthe mounting sections 12 and 12 of the second row, the rows beingcounted from the front. Thus, the intersection 13 is arranged avoidingthe lowest position 1 a which is the maximum load section.

The bottom plate 10 includes a pair of projection sections 15 and 15which project toward the vehicle body 2 and are to be fixed to thevehicle body 2. The projection sections 15 and 15, which forms a pair,are respectively arranged near the mounting sections 12, 12 of thesecond row.

The pair of projection sections 15, 15 are formed so as to be recessedat the upper side of the bottom plate 10. That is, each of theprojection sections 15, 15 which form a pair is provided with a concavesection 15 a which is recessed at the upper side of the bottom plate 10.

The bottom plate 10 further includes an engaging section 18 whichengages with the vehicle body 2. As for the engaging section 18, asshown in FIGS. 4, 5 and 7, a claw section 18 a provided at the positionof the through hole 17 at the rear end part of the bottom plate 10 issuggested, for example. Although it is not shown in the drawings, thevehicle body 2 may be provided with a to-be-engaged section whereengages with the claw section 18 a.

The bottom plate 10 includes a way to improve rigidity of the bottomplate 10 other than the reinforcement sections 11.

As one way, the bottom plate 10 includes a rim reinforcement section 14along the rim of the bottom plate 10 as shown in FIGS. 3, 6 to 8. Therim of the bottom plate refers to the entire periphery edge of thebottom plate 10. That is, by such rim reinforcement section 14, rigidityof the entire periphery edge of the bottom plate 10 can be improved.

Further, as shown in FIGS. 2 to 8, in particular, the rim reinforcementsection 14 includes a main reinforcement section 14 a which is providedalong the periphery edge of the part corresponding to the position wherea passenger sits in the bottom plate 10 and a step section 14 b which isprovided along the entire periphery edge of the bottom plate 10including the main reinforcement section 14 a. The edge of the surfacematerial 3 is fixed to the step section 14 b.

In the bottom plate 10, the part corresponding to the position where apassenger sits is more in the rear than the part where a passenger whodrives the automatic two wheeled vehicle sits (the lowest position 1 a).That is, since the part anterior to the lowest position 1 a is rightabove the fuel tank 2 b, this position is not preferable as the positionwhere a passenger sits.

Therefore, the main reinforcement section 14 a is provided posterior tothe lowest position 1 a in the bottom plate 10 so as to surround theedge of the bottom plate 10. In other words, with the main reinforcementsection 14 a, rigidity at the rim of the part corresponding to theposition where a passenger sits in the bottom plate 10 can be improvedin particular.

On the other hand, the step section 14 b is arranged at the edge that isoutside than the main reinforcement section 14 a. Thereby, rigidity ofthe entire rim of the bottom plate 10 including the main reinforcementsection 14 a can be improved by the step section 14 b. Therefore,rigidity of the bottom plate 10 can also be improved. In other words,even if the automatic two wheeled vehicle is pulled up with a finger bythe rim of the bottom plate 10 when pulling it up, the bottom plate 10can be prevented from deforming due to the weight of the automatic twowheeled vehicle.

As shown in FIG. 5, the step section 14 b includes a bent section 14 cwhich forms a difference in level of the step section 14 b and which isfor positioning the fixation points of the edge 3 a of the surfacematerial 3. That is, the edge of the bottom plate 10 is formed to have astep section by the material being bent. In the step section 14 b whichis formed to have a difference in level, the bent section 14 c is wherean internal angle is formed on the back side of the bottom plate 10. Theedge 3 a of the surface material 3 is fixed to the bent section 14 c bystaples 4.

As a way to improve rigidity of the bottom plate 10, the bottom plate 10includes a reinforcement convex section 16 as shown in FIGS. 6 and 7.

The reinforcement convex section 16 is provided at the center part ofthe bottom plate 10 where surrounded by the plurality of reinforcementsections 11 which are connected to the mounting sections 12, 12 of thethird row. That is, the reinforcement convex section 16 is formedadjacent to the reinforcement sections 11 as a convex section withrespect to the reinforcement sections 11 which are formed to have across-sectional concave shape. Here, the reinforcement convex section 16is formed so as to be recessed at the back side of the bottom plate 10.

On the surface of the diamond shape recessed section at the center ofthe reinforcement convex section 16, a reinforcement rib 16 a forimproving rigidity at the diamond shaped recessed section is formed inan integrated fashion.

Further, as a way to improve rigidity of the bottom plate 10, the bottomplate 10 includes various types of concave and convex sections as shownin FIGS. 6 to 8.

As such various types of concave and convex sections, a belt-like bead19 which is a convex section formed intermittently along the width-wiseC2 of the bottom plate 10, a concave section 19 a formed around thefront side through hole 17 of the bottom plate 10, a concave section 19b which intersects the rear side intersection 13 of the bottom plate 10from left to right, etc. are suggested, for example.

According to the embodiment, the bottom plate 10 includes thereinforcement sections 11 which intersects with the width-wise center C1of the bottom plate 10, at least a part of each reinforcement section 11being arranged obliquely with respect to the front-to-back direction ofthe vehicle seat 1 as an oblique line. However, this is not limitativein anyway. The reinforcement sections 11 may be arranged in thefront-to-back direction and in the left-to-right direction of the bottomplate 10, for example.

Next, the cushion material 20 will be described in detail.

As shown in FIG. 2, the cushion material 20 includes space sections 21(21 a). Since a porous material such as urethane foam as described aboveis used for the cushion material 20, the cushion material 20 includescountless small pores which are generated due to foaming in themanufacturing process. The space sections 21 (21 a) are different fromthe countless small pores. They are not in micro sizes and they areformed intentionally in the cushion material 20.

The space sections 21 are formed at the back side of the cushionmaterial 20 and are opened toward the bottom plate 10. The space section21 a is a hollow section formed inside the cushion material 20. Eitherthe concave sections 21 or the hollow section 21 a is formed in thecushion material 20.

In the embodiment, the concave sections 21 are adapted as the spacesections. Further, it is assumed that a plurality of concave sections 21are formed in the cushion material 20. By the concave sections 21 beingformed in the cushion material 20, the cushion material 20 can bendeasily toward the bottom plate 10 when a passenger sits on the vehicleseat 1.

Each concave section 321 is formed in a dome shape that the sizegradually becomes smaller as approaching the upper side from thereference surface 20 a of the cushion material 20 and that the uppermost part whereof is a curved surface. Since all of the plurality ofconcave sections 21 are formed in such way, the cushion material 20 canbend easily when a load is applied near the concave sections 21.Further, there is an advantage that the cushion material 20 can be takenout easily from a mold which is in a contrasting shape of the concavesections 21 when forming the cushion material 20.

The plurality of concave section 21 are arranged along the front-to-backdirection of the cushion material 20 on the width-wise center C3 of thecushion material 20.

That is, the width-wise center C3 of the cushion material 20 is the partwhere the load of a passenger is likely to be applied. Such width-wisecenter C3 of the cushion material 20 where the load is likely to beapplied can be made to bend easily in the front-to-back direction of thecushion material 20 by the plurality of concave sections 21 which arearranged in a line.

As described above, since the plurality of mounting sections 12 whichare to be fixed to the vehicle body 2 are provided along the innerperiphery on the back side of the bottom plate 10 with spacestherebetween, rigidity of the bottom plate 10 itself can be improved. Aplurality of other concave sections 21 are formed in the cushionmaterial 20 at between the section corresponding to the positions of theplurality of mounting sections 12 and the plurality of concave sections21 arranged along the width-wise center C3 of the cushion material 20.That is, the plurality of concave sections 21 can be formed in thecushion material 20 within the range corresponding to where rigidity ofthe bottom plate is increased by the plurality of mounting sections 12.Therefore, while stably supporting the cushion material 20 by the bottomplate 10, bending of the cushion material 20 can be improved even more.

In FIG. 6, a plurality of mounting section corresponding parts 22 areshown as the parts corresponding to the plurality of mounting sections12 in the cushion material 20.

As described above, the upper surface of the bottom plate 10 and theunder surface of the cushion material 20 are the reference surfaces 10 aand 20 a, respectively. Since the plurality of concave sections 21 areformed on the under surface of the cushion material 20, the surfaceexcluding the plurality of concave sections 21 is the reference surface20 a. Therefore, even if the plurality of concave sections 21 are formedat the back side of the cushion material 20, the bottom plate 10 caneasily support the cushion material 20.

As shown in FIGS. 6 and 16, the plurality of concave sections 21 arearranged in a grid pattern. Further, the plurality of concave sections21 arranged in a grid pattern are arranged in diagonal directions withrespect to the front-to-back direction of the cushion material 20.

In such way, since the plurality of concave sections 21 are arranged ina grid pattern, the plurality of concave sections 21 can be lined neatlyand efficiently within the back side range of the cushion material 20and a great number of concave sections 21 can be formed. Moreover, evenif the plurality of concave sections 21 which are arranged in a gridpattern are arranged in diagonal directions with respect to thefront-to-back direction of the cushion material 20, the plurality ofconcave sections 21 can be lined neatly and efficiently within the backside range of the cushion material 20. Therefore, a great number ofconcave sections 21 can be formed.

Since the concave sections 21 are arranged in diagonal directions, withrespect to two rows of the plurality of concave sections 21 wherein theconcave sections are adjacent to each other, the positions of theplurality of concave sections 21 in one row and the positions of theplurality of concave sections 21 in the other row can be shifted in theleft and right. In other words, the plurality of concave sections 21 canbe arranged in a zigzag pattern. Thereby, for example, the bendingdegree of the cushion material 20 can be improved by making the size ofthe plurality of concave sections 21 be larger. Further, even moreconcave sections 21 can be arranged densely by making the plurality ofconcave sections 21 be closer to each other.

As shown in FIG. 17, the cushion material 20 includes a pair of expectedischium sections 23, 23 as regions in the cushion material 20 whereexpected to be the positions corresponding to the ischium position of apassenger. In other words, in the cushion material 20, the pair ofexpected ischium sections 23, 23 are parts where the load of a passengeris likely to be applied (the arrows Y1 in FIG. 18).

In the embodiment, the plurality of concave sections 21 are arranged atpositions avoiding the pair of expected ischium sections 23, 23.Thereby, the reference surface 20 a is to be arranged at the positionsof the pair of expected ischium sections 23, 23. Thus, the ischium of apassenger can be supported stably.

Further, one of the plurality of concave sections 21 is arranged betweenthe expected ischium sections 23, 23 which form the pair. That is, asdescribed above, the cushion material 20 can be made lighter whilestably supporting the positions of the pair of expected ischium sections23, 23 by the reference surface 20 a. Moreover, the parts where the loadof a passenger is likely to be applied in the cushion material 20 can beprevented from having trouble bending.

In the embodiment, the reference surface 20 a side periphery of theconcave section 21 arranged between the expected ischium sections 23, 23which form the pair is supported by the bottom plate 10 as shown in FIG.18. In particular, the reference surface 20 a side periphery of suchconcave section 21 is supported by the turning sections 11 a, 11 a ofthe reinforcement sections 11, 11 which are positioned under theexpected ischium sections 23, 23 which form the pair.

That is, since the edge of the concave section 21 between the expectedischium sections 23, 23 which form the pair, these sections being wherethe load of a passenger is likely to be applied, is supported by theturning sections 11 a, 11 a in the bottom plate 10 where rigidity ishigh, vicinity of the pair of expected ischium sections 23, 23 can besupported even more stably while maintaining likeliness of bending atvicinity of the pair of expected ischium sections 23, 23 by the concavesection 21.

As shown in FIG. 18, the concave sections 21, 21 are respectivelyarranged on the right and the left of the concave section 21 arrangedbetween the expected ischium sections 23, 23 which form the pair. In theembodiment, with respect to these left and right concave sections 21,21, only the outside parts of the reference surface 20 a sideperipheries of the left and right concave sections 21, 21 are supportedby the bottom plate 10.

In a case of a two wheeled vehicle, body weight shifts toward thecurving direction when entering a curve (see arrows Y2 in FIG. 18). Atthis time, by the outside parts of the reference surface 20 a sideperipheries of the left and right concave sections 21, 21, the positionsin the cushion material 20 where the load is likely to be applied whenentering a curve are supported. Therefore, sitting can be stable whenentering a curve.

In FIG. 18, the oval shape at the upper center of the cushion material20 and the three half circle shapes below the oval shape are imagesexpressing the passenger load applied to the cushion material 20. Thearrows Y1 and Y2 indicate the directions of the passenger load.

As shown in FIG. 18, the cushion material 20 is further provided withinsertion sections 24, 24 which are to be inserted in to the concavesections 15 a, 15 a of the projection sections 15, 15 of the bottomplate 10 at further outside of the left and right concave sections 21,21. These insertion sections 24, 24 are formed so as to protrude moredownward than the reference surface 10 a of the bottom plate 10.

Since the insertion sections 24, 24 are provided further outside of theleft and right concave sections 21, 21, the load can be supported by theinsertion sections 24, 24 when the automatic two wheeled vehicle entersa curve.

At predetermined parts of the cushion material 20, the reference surface20 a of the cushion material 20 is arranged to vertically face thereinforcement sections 11 of the bottom plate 10.

Thereby, when the cushion material 20 bends, the cushion material 20 cansink more downward than the reference surface 20 a by using thedifference in level of the reinforcement sections 11, i.e. the turningsections 11 a and the wall sections lib. Therefore, the cushion material20 can bend more easily.

That is, not only the reference surface 10 a of the bottom plate 10 andthe reference surface 20 a of the cushion material 20 are tightly incontact with each other, but also the reference surface 20 a partiallysinks in to the recesses of the reinforcement sections 11 which are in across-sectional concave shape. Thus, the cushion material 20 can beprevented from having trouble bending.

Further, at predetermined parts of the cushion material 20, the lengthof the parts in the reference surface 20 a of the cushion material 20corresponding to the straight lines L that connect center points of theconcave sections 21, 21 which are adjacent to each other in theleft-to-right direction of the vehicle seat 1 is approximately equal tothe width of the reinforcement sections 11.

Thereby, the parts in the reference surface 20 a corresponding to thestraight lines L which connect the center points of the concave sections21, 21 which are adjacent to each other in the left-to-right directionof the vehicle seat 1 can be prevented from sinking in to the recessesof the reinforcement sections 11 and the cushion material 20 can beprevented from partially caving in.

That is, even if the reinforcement sections 11 are in a cross-sectionalconcave shape that are recessed at the upper side of the bottom plate10, if the width of the reinforcement sections 11 and the length of theparts corresponding to the straight lines L in the reference surface 20a are approximately equal, the parts corresponding to the straight linesL do not sink in the recesses of the reinforcement sections 11.Therefore, at the above parts in the cushion material 20, the cushionmaterial 20 can be prevented from partially caving in.

Even if the bottom plate 10 is provided with a plurality ofreinforcement sections 11 and even if the cushion material 20 isprovided with a plurality of concave sections 21, generally, the bottomplate 10 and the cushion material 20 are in a state where the referencesurfaces 10 a and 20 a are in contact with each other. Therefore, it isexpected that the bending degree of the cushion material is uniformoverall.

As shown in FIGS. 6 and 11 to 14, the cushion material 20 includes edgeconcave sections 25, 25 provided at parts above the main reinforcementsection 14 a of the bottom plate 10, the edge concave sections 25, 25being respectively arranged near the two side edges of the cushionmaterial 20. Spaces are formed between the edge concave sections 25, 25and the main reinforcement section 14 a.

Each of the edge concave sections 25, 25 includes ribs 25 a which areformed at a plurality of points along the front-to-back direction of thevehicle seat 1.

With such edge concave sections 25, 25, the cushion material 20 can bemade lighter. When the vehicle seat 1 is to be used as a two-seater,since the parts corresponding to the edge concave sections 25, 25 arelikely to bend, sitting properties thereof, including a case where thevehicle seat 1 is used as a two-seater, can be improved.

With respect to the plurality of ribs 25 a, the under surfaces thereofare in contact with the upper surface of the main reinforcement section14 a. Therefore, the load of a passenger who sits behind the passengerwho drives the automatic two wheeled vehicle can be supported easily.

Further, as shown in FIGS. 4 to 15, the cushion material 20 includes anabutting step section 26 which is provided around the entire peripheryedge of the cushion material 20 and which abuts the upper side of thestep section 314 b of the bottom plate 10. That is, the abutting stepsection 26 is formed so as to correspond to the shape of the upper sideof the step section 14 b and is tightly in contact with the step section14 b.

By the step section 14 b and the abutting step section 26 being incontact with each other, the entire periphery edge of the bottom plate10 and the entire periphery edge of the cushion material 20 are in aunified state. Therefore, when folding the edge 3 a of the surfacematerial 3 in to the back side of the bottom plate 10 and fixating theedge 3 a thereto, the surface material 3 can easily cover the edge ofthe bottom plate 10 and the edge of the cushion material 20.

Since a porous material such as urethane foam is used for the cushionmaterial 20 as described above, the air goes through, enters and exits,the micro pores of the cushion material 20 when the cushion materialbends and recovers from the bent state. Further, as described above, thereference surface 10 a of the bottom plate 10 where the plurality ofreinforcement sections 11 are formed and the reference surface 20 a ofthe cushion material 20 wherein the plurality of concave sections 21 areformed are in contact with each other.

Therefore, one concave section 21 of the plurality of concave sections21 and smother concave section 21 which is different from the oneconcave section 21 are in communication with each other through thereinforcement section 11 formed so as to be recessed at the upper sideof the bottom plate 10. Thereby, when the cushion material 20 bends, theair can be let out to another concave section 21 from the one concavesection 21 through the reinforcement sections 11. Therefore, the cushionmaterial 20 can bend more easily.

Since the cushion material 20 is supported by the upper surface of thebottom plate 10 and is covered with the surface material 3, there may bea case where the air flow is blocked. In order to control this, theopening 17 is formed in the bottom plate 10 as an air passage.

According to the embodiment, since the cushion material 20 is providedwith the concave sections 21, the cushion material 20 can be madelighter even without making the cushion material 20 be thinner as in aconventional case. Thereby, while maintaining a stable sitting, thevehicle seat 1 can be made lighter. Further, since a plurality ofconcave sections 21 are formed in the cushion material 20, the cushionmaterial 20 can bend more easily.

Second Embodiment

In FIG. 19, the reference numeral 301 indicates a vehicle seat providedwith a bottom plate structure according to the present invention. Thevehicle seat 301 of the embodiment is to be used in an automatic twowheeled vehicle.

Here, the vehicle seat is not limited to the seats used in automatic twowheeled vehicles as in the embodiment. The vehicle seat includes seatsof two wheeled vehicles such as motorcycles, scooters, snow mobiles andpersonal watercrafts, three wheeled buggies, straddle type vehicles,seats of construction machines, four wheeled vehicles, etc.

The vehicle seat 301 includes a bottom plate 310 which is provided onthe vehicle body 302 of the automatic two wheeled vehicle, a cushionmaterial 320 which is supported by the upper surface of the bottom plate310 and a surface material 303 which covers the bottom plate 310 and thecushion material 320. That is, the vehicle seat 301 is formed by thecushion material 320 being supported on the bottom plate 310 and thecushion material 320 and the bottom plate 310 being covered with thesurface material 303.

The parts of the vehicle body 302 where the bottom plate 310 is to befixed are, in particular, the seat rail 302 a which is laid on thevehicle body 302 and the fuel tank 302 b in front of the vehicle seat301.

The bottom plate 310 is formed by a resin material such aspolypropylene, polyvinylchloride, etc., and is formed in a shapecorresponding to the shape of the vehicle body 302 of the automatic twowheeled vehicle. The bottom plate 310 is attached to the vehicle body302.

The bottom plate 310 of the embodiment is formed by using polypropyleneas a material, for example. In order to fixate the bottom plate 310 tothe vehicle body 302 of the automatic two wheeled vehicle, thepolypropylene is to be especially hard. The bottom plate 310 may beprovided with clasps or the like necessary to be fixed to the vehiclebody 302 of the automatic two wheeled vehicle.

The cushion material 320 is formed of a soft foam material such as, forexample, urethane foam, polypropylene foam or polyethylene foam. As forthe cushion material 320 of the embodiment, for example, urethane foamis used.

Since the cushion material 320 is supported by the upper surface of thebottom plate 310, the under surface of the cushion material 320 isformed in a shape reflecting the shape of the upper surface of thebottom plate 310. Thereby, the cushion material 320 can be supportedstably by the upper surface of the bottom plate 310. The surfaces of thebottom plate 310 and the cushion material 320 which contact each other,that is, the upper surface of the bottom plate 310 and the under surfaceof the cushion material 320 are referred to as the reference surfaces310 a and 320 a, respectively.

The cushion material 320 is formed so that the part in the upper surfacethereof where a passenger who drives the automatic two wheeled vehiclesits is lower than the other portion when seen from a side. This part isreferred to as the lowest position 301 a that is the lowest along thewidth-wise center C2 of the vehicle seat 301 in the front-to-backdirection of the vehicle seat 301. The part near the lowest position 301a corresponds to the ischium position of the passenger who drives theautomatic two wheeled vehicle and is the maximum load section where themaximum passenger load is applied in the vehicle seat 301.

The surface material 303 constitutes the sitting surface of the vehicleseat 301. The surface material 303 is where comes in contact with apassenger and is formed by a resin material such as polypropylene,polyvinylchloride or the like. As for the surface material 303 of theembodiment, for example, a hard material made of polypropylene is used.

As shown in FIG. 21, the edge 303 a of the surface material 303 isfolded in to the back side of the bottom plate 310 and is fixed to theback side of the bottom plate 310 by staples 304.

The edge 303 a of the surface material 303 refers to the entireperiphery edge of the surface material 303. Therefore, the edge 303 a ofthe surface material 303 is fixed along the entire periphery edge of thebottom plate 310.

Next, the bottom plate 310 will be described in more detail.

The bottom plate 310 includes a plurality of reinforcement sections 311which intersect with the width-wise center C1 of the bottom plate 310,each of which having at least a part thereof arranged obliquely withrespect to the front-to-back direction of the vehicle seat as an obliqueline. That is, the reinforcement sections 311 are not merely arrangedvertically and horizontally (from front to back and from side to side)in the bottom plate 310. By the reinforcement sections 311 includingparts that are arranged obliquely, it is expected to obtain rigidity inthe front-to-back direction and the left-to-right direction.

The reinforcement sections 311 are in a bead shape bulged at the backside of the bottom plate 310 and recessed at the upper side of thebottom plate 310. That is, as shown in FIGS. 20, 28, etc., each of thereinforcement sections 311 is formed in a cross-sectional concave shapeand includes a pair of side walls 311 b, 311 b each of which formed bybeing bent downward from the upper surface of the bottom plate 310 and abottom which is formed in an integrated fashion being bridged betweenthe lower edges of the side walls 311 b, 311 b which form a pair.Corners where turned downward from the upper surface of the bottom plate310 are referred to as turning sections 311 a and are the parts havinghigh rigidity in the reinforcement sections 311.

The upper side of the bottom plate 310 includes the upper surface of thebottom plate 310 and the surface of the step section 314 b (describedlater) which is formed along the entire periphery edge of the bottomplate 310 and which is bent toward the vehicle body 302 than the uppersurface of the bottom plate 310. On the other hand, the back side of thebottom plate 310 is the back of the upper side of the bottom plate 310and includes the under surface of the bottom plate 310 and the back sideof the step section 314 b.

According to the above described reinforcement sections 311, aconcave-convex figure is formed in the bottom plate 310 leading toimprovement in rigidity of the bottom plate 310. Further, since thebottom plate 310 can be reinforced in a state where the upper sidethereof is partially recessed, bending of the cushion material 320 whichis supported by the upper surface of the bottom late 310 is notinhibited comparing to a case where the bottom plate 310 is reinforcedin a state where the upper side thereof is partially bulged. Therefore,a comfortable sitting condition can be provided to a passenger.

Although the reinforcement sections 311 are formed in a cross-sectionalconcave shape in the embodiment, this is not limitative in any way. Thereinforcement sections 311 may be formed in a protruding shape such as arib on the back side of the bottom plate 310.

As shown in FIGS. 22, 23, 25, etc., the bottom plate 310 is providedwith a plurality of mounting sections 312 through which the bottom plate310 is fixed to the vehicle body 302, the mounting sections 312 beingformed on the back side of the bottom plate 310 with spacestherebetween.

The mounting sections 312 refer to the parts which are to be fixed tothe vehicle body 302 themselves and also to elastic members such asrubbers attached to the above parts and the parts where the elasticmembers are to be attached.

Further, as shown in FIGS. 26, 27, 31 and 32, the elastic members areprovided with projecting inserting sections, and they are fixed to thebottom plate 310 by inserting the inserting sections in the insertionholes formed in the bottom plate 310 to engage the inserting sectionsand the insertion holes. For example, the elastic members may be fixedto the bottom of the bottom plate 310 by welding or the like.

In each of the elastic members of the mounting sections 312, a bolt holeis formed near the center thereof. The bottom plate 310 can be fixed tothe seat rail 302 a of the vehicle body 302 by the bolts which areinserted through the bolt holes.

With respect to a part where the distance from the bottom plate 310 tothe seat rail 302 a is long, a leg section 312 a is formed on the backside of the bottom plate 310 in an integrated fashion and an elasticmember of the mounting section 312 is fixed at the tip of the legsection 312 a. That is, such mounting section 312 includes the legsection 312 a.

The leg section 312 a is formed so as to be recessed at the upper sideof the bottom plate 310. That is, the leg section 312 a includes aconcave section 312 b which is recessed at the upper side of the bottomplate 310.

The plurality of mounting sections 312 of the embodiment aresymmetrically arranged at eight points on the back side of the bottomplate 310. Pairs of mounting sections 312 and 312 are arranged in fourrows along the front-to-back direction of the bottom plate 310, themounting sections 312 and 312 forming each pair are arranged widthwise.

Here, among the plurality of mounting sections 312, the mountingsections 312, 312 which are provided at the front end part (in the firstrow counting from the front) of the bottom plate 310 abuts the fuel tank302 b of the vehicle body 302 as shown in FIG. 25. These mountingsections 312, 312 of the first row are not fixed to the fuel tank 302 bby bolts and are not fixed to the seat rail 302 a.

The reinforcement sections 311 are arranged between the plurality ofmounting sections 312, 312 which are apart from each other. In theembodiment, the bottom plate 310 is provided with a plurality ofreinforcement sections 311 as shown in FIGS. 22 and 23. The bottom plate310 further includes intersections 313 formed by the plurality ofreinforcement sections 311 intersecting with each other. That is, theplurality of reinforcement sections 311 are made to intersect with eachother and are arranged in different directions. Comparing to a casewhere the plurality of reinforcement sections do not intersect with eachother, in the above arrangement, rigidity of the bottom plate can beimproved more.

The plurality of reinforcement sections 311 of the embodiment aresymmetrically arranged when being arranged in different directions.

Further, in the embodiment, the bottom plate 310 is provided with aplurality of intersections 313.

On the upper side of one of the plurality of intersections 313 and 313,reinforcement ribs 313 a for improving rigidity at the intersection 313are formed in an integrated manner.

The plurality of intersections 313 and 313 are arranged along thewidth-wise center C1 of the bottom plate 310, and rigidity at thewidth-wise center C1 in the bottom plate 310 where load is likely to beapplied can be improved.

Further, the plurality of intersections 313 and 313 are arrangedavoiding the lowest position 301 a in the bottom plate 310. The lowestposition 1 a in the bottom plate 310 is the maximum load section where agreat portion of the load of a passenger is applied. The intersections313 are the parts in the bottom plate 310 where rigidity is improved.Therefore, the position where the passenger load is applied greatly andthe parts where rigidity is improved by the intersections 313 do notoverlap. Thereby, the passenger can be prevented from feeling a stronguncomfortable pressure and a comfortable sitting condition can beprovided to the passenger.

In the embodiment, as shown in FIG. 23, the front side intersection 313of the plurality of intersections 313 and 313 is disposed between themounting sections 312 and 312 of the second row and the mountingsections 312 and 312 of the third row, the rows being counted from thefront. On the other hand, the lowest position 301 a, which is themaximum load section, is between the mounting sections 312 and 312 ofthe first row and the mounting sections 312 and 312 of the second row,the row being counted from the front. Thus, the intersection 313 isarranged avoiding the lowest position 301 a which is the maximum loadsection.

The bottom plate 310 includes a pair of projection sections 315 and 315which project toward the vehicle body 302 and are fixed to the vehiclebody 302. The projection sections 315 and 315, which form a pair, arearranged near the mounting sections 312, 312 of the second row.

The pair of projection sections 315, 315 are formed so as to be recessedat the upper side of the bottom plate 310. That is, each of theprojection sections 315, 315 which form a pair is provided with aconcave section 315 a which is recessed at the upper side of the bottomplate 310.

The bottom plate 310 is bent from near the mounting sections 312, 312 ofthe second row. If the part posterior to the mounting sections 312, 312of the second row is the main surface section 101 and the part anteriorto the mounting sections 312, 312 of the second row is the sub surfacesection 102, the sub surface section 102 which is arranged in front ofthe main surface section 101 is tilted upward with respect to the mainsurface section 101. The bent section between the main surface section101 and the sub surface section 102 is the bent section 103.

As shown in FIG. 27, a rib 104 which extends in the left-to-rightdirection is arranged between the mounting sections 312, 312 of thesecond row at the back side of the bent section 103 in the bottom plate310.

At near the mounting sections 312, 312 of the second row, thereinforcement sections 311, 311 are arranged and the reinforcementsections 311, 311 form a convex V shape when seen from the above, thelower tip of the V shape pointing backward as shown in FIG. 23. Ends ofthe reinforcement sections 311, 311, which form a V shape, are arrangednear the mounting sections 312, 312 of the second row. In such way, atop view V shaped bead (reinforcement sections 311, 311) arrangedbetween the left and right mounting sections 312, 312 of the second rowis formed.

As shown in FIGS. 23 and 27, at the bent section 103 of the bottom plate310, wall sections 105, 105 which extend vertically are formed so as toface each other in the left-to-right direction, the wall sections beingformed along the front-to-back direction. In particular, the wallsections 105, 105 are formed perpendicularly and the lower ends thereofcontinue to the step section 314 b.

At the front and rear parts of the bottom plate 310, openings 317, 318are respectively formed at the positions facing the vehicle body 302.

As shown in FIGS. 38 and 39, the opening 317 at the front end part isfor preventing the bottom plate 310 from interfering with an locksection 200 of the fuel tank 302 b of the vehicle 2. For example, when aperson sits on the vehicle seat 301, it is expected that the bottomplate 310 bends with the cushion material 320. The size of the opening317 is set so that the bottom plate 310 can be prevented frominterfering with the lock section 200 of the vehicle body 302 even ifthe bottom plate 310 bends.

As shown in FIGS. 40 and 41, at the opening 318 at the rear end part, anengaging section 318 a which engages with the vehicle body 302 isformed. Here, the engaging section 318 a is a projection plate whichextends backward from the front part of the opening 318. This engagingsection 318 a is to engage with the to-be-engaged section 201 of thevehicle body 302.

The bottom plate 310 includes a way to improve rigidity of the bottomplate 310 other than the reinforcement sections 311.

As one way, the bottom plate 310 includes a rim reinforcement section314 that is provided along the periphery edge of the bottom plate 310 asshown in FIGS. 21, 24 to 26. The rim of the bottom plate refers to theentire periphery edge of the bottom plate 310. That is, by such rimreinforcement section 314, rigidity of the entire periphery edge of thebottom plate 310 can be improved.

Further, as shown in FIGS. 20 to 26, the rim reinforcement section 314includes a main reinforcement section 314 a which is provided along theperiphery edge of the part corresponding to the position where apassenger sits in the bottom plate 310 and a step section 314 b which isprovided along the entire periphery edge of the bottom plate 310including the main reinforcement section 314 a. The edge of the surfacematerial 303 is fixed to the step section 314 b.

In the bottom plate 310, the part corresponding to the position where apassenger sits is more in the rear than the part where a passenger whodrives the automatic two wheeled vehicle sits (the lowest position 301a). That is, since the part anterior to the lowest position 1 a is rightabove the fuel tank 302 b, this position is not preferable as a positionwhere a passenger sits.

Therefore, the main reinforcement section 314 a is provided posterior tothe lowest position 301 a in the bottom plate 301 so as to surround theedge of the bottom plate 310. In other words, with the mainreinforcement section 314 a, rigidity at the rim of the partcorresponding to the position where a passenger sits in the bottom plate310 is improved in particular.

On the other hand, the step section 314 b is arranged at the edge thatis outside than the main reinforcement section 314 a. Thereby, rigidityof the entire rim of the bottom plate 310 including the mainreinforcement section 314 a can be improved by the step section 314 b.Therefore, rigidity of the bottom plate 310 can also be improved. Inother words, even if the automatic two wheeled vehicle is pulled up witha finger by the rim of the bottom plate 310 when pulling it up, thebottom plate 310 can be prevented from deforming due to the weight ofthe automatic two wheeled vehicle.

As shown in FIG. 23, the step section 314 b includes a bent section 314c which forms a difference in level of the step section 314 b and whichis for positioning the fixation points of the edge 303 a of the surfacematerial 303. That is, the edge of the bottom plate 310 is formed tohave a step section by the material being bent. In the step section 314b which is formed to have a difference in level, the bent section 314 cis where an internal angle is formed on the back side of the bottomplate 310. The edge 303 a of the surface material 303 is fixed to thebent section 314 c by staples 304.

As a way to improve rigidity of the bottom plate 310, the bottom plate310 includes a reinforcement convex section 316 as shown in FIGS. 22, 23and 31.

The reinforcement convex section 316 is provided at the center part ofthe bottom plate 310 where surrounded by the plurality of reinforcementsections 311 which are connected to the mounting sections 312, 312 ofthe third row. That is, the reinforcement convex section 316 is formedadjacent to the plurality of reinforcement sections 311 as a convexsection with respect to the reinforcement sections 311 which are formedto have a cross-sectional concave shape. Here, the reinforcement convexsection 316 is formed so as to be recessed at the back side of thebottom plate 310.

On the surface of the diamond shape recessed section at the center ofthe reinforcement convex section 316, a reinforcement rib 316 a forimproving rigidity at the diamond shaped recessed section is formed inan integrated fashion.

Further, as a way to improve rigidity of the bottom plate 310, thebottom plate 310 includes various types of concave and convex sectionsas shown in FIGS. 24 to 26.

As such various types of concave and convex sections, a belt-like bead319 which is a convex section formed intermittently along the width-wisecenter C2 of the bottom plate 310, a concave section 19 a formed aroundthe front side opening 317 of the bottom plate 310, a concave section319 b which intersects the rear side intersection 313 of the bottomplate 310 from left to right, a concave section 319 c which is formedaround the rear side opening 318 of the bottom plate 310, etc. aresuggested, for example. With the concave sect ions 319 a and 319 c, theparts around of the openings 317 and 318 are in a bead shape.

The reinforcement sections 311 of the embodiment intersect with thewidth-wise center C1 of the bottom plate 310, and at least apart of eachreinforcement section 311 is arranged obliquely with respect to thefront-to-back direction of the vehicle seat 301 as an oblique line.However, such configuration is not limitative in any way, and thereinforcement sections 311 may be arranged in the front-to-backdirection and in the left-to-right direction of the bottom plate 310,for example.

Next, the cushion material 320 will be described in detail.

As shown in FIG. 20, the cushion material 320 includes concave sections321 as spaces. Since a porous material such as urethane foam asdescribed above is used for the cushion material 320, the cushionmaterial 320 includes countless small pores which are generated due tofoaming in the manufacturing process. The concave sections 321 aredifferent from the countless small pores. They are not in micro sizesand they are formed intentionally in the cushion material 320.

The concave sections 321 are formed at the back side of the cushionmaterial 320 and are opened toward the bottom plate 310.

The cushion material 320 is provided with a plurality of concavesections 321. By the concave sections 321 being formed in the cushionmaterial 320, the cushion material 320 can easily bend toward the bottomplate 310 when a passenger sits on the vehicle seat 301. The partsbetween the individual concave sections 321 that are not recessed arewall sections 327.

Each concave section 321 is formed in a shape that the size graduallybecomes smaller as approaching the upper side from the lower side. Inparticular, inside of each concave section 321 is a concave curvedsurface which is recessed upward from the reference surface 320 a of thecushion material 320. In such way, the concave sections 321 are in adome shape. Since all of the plurality of concave sections 321 areformed in such way, the cushion material 320 can bend easily when a loadis applied near the concave sections 321. Further, there is an advantagethat the cushion material 320 can be taken out easily from a mold whichis in a contrasting shape of the concave sections 321 when forming thecushion material 320.

The shape of the openings at the lower ends of the concave sections 321is a circle shape as shown in FIG. 17. Here, the shape of the openingsof the concave sections 321 is not limited to a circle shape and may bean oval shape.

The plurality of concave sections 321 are arranged along thefront-to-back direction of the cushion material 320 on the width-wisecenter C3 of the cushion material 320.

That is, the width-wise center C3 of the cushion material 320 is thepart where the load of a passenger is likely to be applied. Suchwidth-wise center C3 of the cushion material 320 where the load islikely to be applied can be made to bend easily in the front-to-backdirection of the cushion material 320 by the plurality of concavesections 321 which are arranged in a line.

As described above, since the plurality of mounting sections 312 whichare to be fixed to the vehicle body 302 are provided, along the innerperiphery on the back side of the bottom plate 310 with spacestherebetween, rigidity of the bottom plate 310 itself can be improved. Aplurality of other concave sections 321 are formed in the cushionmaterial 320 at between the section corresponding to the positions ofthe plurality of mounting sections 312 and the plurality of concavesections 321 arranged along the width-wise center C3 of the cushionmaterial 320. That is, the plurality of concave sections 321 can beformed in the cushion material 321 within the range corresponding towhere rigidity of the bottom plate 310 is increased by the plurality ofmounting sections 312. Therefore, while stably supporting the cushionmaterial 320 by the bottom plate 310, bending of the cushion material320 can be improved even more.

In FIG. 24, a plurality of mounting section corresponding parts 322 areshown as the parts corresponding to the plurality of mounting sections312 in the cushion material 320.

As described above, the upper surface of the bottom plate 310 and theunder surface of the cushion material 320 are the reference surfaces 310a and 320 a, respectively. Since the plurality of concave sections 321are formed on the under surface of the cushion material 320, the surfaceexcluding the plurality of concave sections 321 is the reference surface320 a. Therefore, even if the plurality of concave sections 321 areformed at the back side of the cushion material 320, the bottom plate310 can easily support the cushion material 320.

As shown in FIGS. 24 and 34, the plurality of concave sections 321 arearranged in a grid pattern via the wall sections 327. Further, theplurality of concave sections 321 arranged in a grid pattern arearranged in diagonal directions with respect to the front-to-backdirection of the cushion material 320.

In such way, since the plurality of concave sections 321 are arranged ina grid pattern, the plurality of concave sections 321 can be linedneatly and efficiently within the back side range of the cushionmaterial 320 and a great number of concave sections 321 can be formed.Moreover, even if the plurality of concave sections 321 which arearranged in a grid pattern are arranged in diagonal directions withrespect to the front-to-back direction of the cushion material 320, theplurality of concave sections 321 can be lined neatly and efficientlywithin the back side range of the cushion material 320. Therefore, agreat number of concave sections 321 can be formed.

Since the concave sections 321 are arranged in diagonal directions, withrespect to two rows of the plurality of concave sections 321 wherein theconcave sections are adjacent to each other in their front and back, thepositions of the plurality of concave sections 321 in one row and thepositions of the plurality of concave sections 321 in the other row canbe shifted in the left and right. In other words, the plurality ofconcave sections 321 can be arranged in a zigzag pattern. Thereby, forexample, the bending degree of the cushion material 320 can be improvedby making the size of the plurality of concave sections 321 be larger.Further, even more concave sections 321 can be arranged densely bymaking the plurality of concave sections 321 be closer to each other.

As shown in FIG. 35, concave sections 321 a are provided at the partcorresponding to the bent section 103 of the bottom plate 310. In FIG.35, the bent section 103 is shown in a two-dot chain line forconvenience sake. However, the bent section 103 has a region of acertain extent. Although a case where two concave sections 321 a areprovided at the part corresponding to the bent section 103 is describedin the present invention, it is sufficient that at least one concavesection 321 a is provided at the section. Further, it is preferred thatthe deepest point of the concave curved surface of each concave section321, i.e. the inner apex thereof, is to be arranged on the bent section103. The two concave sections 321 a which are provided at the partcorresponding to the bent section 103 overlap with the two ends of thetop view V shaped bead (reinforcement sections 311, 311).

The ischium of a passenger is likely to be positioned on the bentsection 103. Therefore, the two concave sections 321 a provided at thepart corresponding to the bent section 103 face the ischium of thepassenger.

Further, concave sections 321 b and 321 c are provided in the front ofand behind the concave sections 321 a provided at the part correspondingto the bent section 103 with wall section 327 therebetween. One frontside concave section 321 b is arranged in the front of and between thetwo concave sections 321 a. Three rear side concave sections 321 c arearranged behind and between the two concave sections 321 a.

The concave section 321 b and the concave section 321 d are provided atthe parts corresponding to the openings 317 and 318 of the bottom plate310, respectively. In particular, the concave section 321 b is providedat the part corresponding to the front side opening 317 of the bottomplate 310. Approximately front half of the concave section 321 boverlaps with the opening 317. The concave sections 321 e and 321 c areprovided in the front of and behind the concave section 321 b with wallsections 327 therebetween. The periphery of the opening 317 faces thewall sections 327.

On the other hand, the concave section 321 d is provided at the partcorresponding to the rear side opening 318 of the bottom plate 310. Theback part of the concave section 321 d overlaps with the opening 318.

Next, operation of the embodiment will be described.

In FIG. 36, the grid section K shows the deformation level of individuallayers in the cushion material 320. As shown in FIG. 36, the cushionmaterial 320 is not bent before a passenger sits thereon, and the layersin the grid section K maintain the normal state where the individuallayers are in the same size.

In FIG. 37, the two-dot chain line shows the cushion material 320 beforea passenger sits thereon. When the cushion material 320 bends due to apassenger sitting thereon as shown in FIG. 37, as shown in the gridsection K, the degree of bending becomes smaller as moving up to theupper layers from the lowest layer. Since stress concentrates at thewall sections 327 whose cross-section areas are small, the degree ofbending is greater in the lowest layer comparing to the upper layers.

It has been said that, in general, a passenger can sit comfortably whenhe/she can feel the hardness to a certain extent in a vehicle seat of atwo wheeled vehicle or the like. Therefore, if the cushion material 320is formed so as to bend at a part other than the upper layers thereof,the cushion material 320 is not likely to bend in the upper layersthereof and the passenger can feel a certain level of hardness. On theother hand, since a part other than the upper layers of the cushionmaterial 320 is more likely to bend comparing to the upper layers, thispart can absorb the vibration and the like caused by the unevenness ofthe road surface. Therefore, even if the cushion material 320 is madethinner and the vehicle seat is made lighter, a stable sitting can bemaintained.

Since the cushion material 320 is formed so that it bends at the lowestlayer part thereof, the bending is to start at the lowest layer partthat is most distanced from the upper layer part. Therefore, the upperlayer part can be inhibited from deforming with the bending of thelowest layer part, and the comfortable sitting can be prevented frombecoming uncomfortable due to bending.

Since the plurality of concave sections (space sections) 321, each ofwhich has a shape that becomes smaller as approaching the upper sectionthereof from the lower section thereof, are formed in the cushionmaterial 320, the lowest layer part of the cushion material 320 beingthe lower ends of the concave sections 321, the cross-section area ofthe lowest layer part is smaller than the cross-section area of theupper layer part. Thereby, stress is concentrated at the lowest layerpart, and thus, the lowest layer part is even more likely to bend.

Since the cushion material 320 has hollow spaces therein by forming theconcave sections 321, the cushion material 320 can be made lighter.

Moreover, since the lower ends of the concave sections 321 are opened,they can deform in their circumferential direction with increased degreeof freedom and the lowest layer part can bend even more.

Since the shape of the opening sections of the concave sections 321 is acircle shape or an oval shape, stress can be dispersed more comparing toa case where corners are formed, at the rims of the opening sections,and thus, breaking can be prevented.

Since the inner surfaces of the concave sections 321 are concave curvedsurfaces which are recessed upward, stress can be dispersed due to theinner surfaces of the concave sections 321 being curved surfaces, andthus, breaking can be prevented.

The bent section 103 between the main surface section 101 and the subsurface section 102 of the bottom plate 310 is where the buttocks of apassenger are to be placed in most cases. That is, the passenger can sitmore comfortably if the cushioning properties at this section areimproved. Further, if at least one concave section 321 a is formed atthe bent section 103 in the cushion material 320 as described above, thecushioning properties can be ensured by the concave section 321 a evenif the cushion material 320 is made thin, and thus, a stable sitting canbe maintained.

Since the concave section 321 a is formed at the part corresponding tothe ischium of the passenger who sits on the bent section 103, thecushioning properties with respect to the ischium of the passenger canbe ensured, and thus, the passenger can sit more comfortably.

Since the space sections 321 b and 321 c are also provided in the frontof and behind the concave section 321 a at the part corresponding to thebent section 103, even higher cushioning properties can be ensured.Further, since the wall sections 327 are provided between the concavesections 321 a, 321 b and 321 c, the wall sections 237 regulates excessbending of the cushion material 320, and thus, a stable cushioningproperties can be ensured.

Since the inner surface of the concave section 321 a at the partcorresponding to the bent section 103 is a concave curved surface thatis recessed upward and the deepest point of the concave curved surfaceis arranged on the bent section 103, stress due to a passenger sittingon the bent section 103 can be dispersed efficiently.

Since the wall sections 105, 105 that extend vertically are formed alongthe front-to-back direction so as to face each other at the left sideand the right side of the bottom plate 310 on the bent section 103,rigidity at the bent section 103 in the front-to-back direction can beimproved by the wall sections 105, 105. If rigidity in the front-to-backdirection of the bent section 103 is improved, twisting of the bottomplate 310 can be prevented, and thus, more comfortable sitting can beprovided.

Since the rib 104 that extends from the left to right is provided on theback side between the left and right mounting sections 312, 312 of thesecond row and the top view V shape bead (reinforcement sections 311,311) is arranged on the upper side, rigidity of the left and rightmounting sections 312, 312 can be improved, and thus, stability inattachment to the vehicle body can be improved.

Since the top view V shaped bead (reinforcement sections 311, 311) isarranged so as to overlap with the concave sections 321 a at the partcorresponding to the bent section 103 of the cushion material 320, thebead guides the entering and exiting of the air in the concave sections321 caused by the bending of the cushion material 320, and thus, thecushion material 320 can bend smoothly.

The parts near the openings 317 and 318 in the bottom plate 310 are theparts not directly relevant to supporting of the vehicle seat 301.Therefore, as described above, even if the concave sections 321 b and321 d are formed at the positions facing the openings 317 and 318 in thecushion material 320, stability of the vehicle seat 301 is maintained,and thus, a stable sitting can also be maintained.

Since the concave sections 321 e and 321 a are also provided in thefront of and behind the concave section 321 b which is at the positionfacing the opening 317, the plurality of concave sections 321 a, 321 band 321 e can be arranged near the opening 317 which is not directlyrelevant to supporting the vehicle seat 1, and thus, the cushionmaterial 320 can be made even more lighter.

Since the wall sections 327 between the plurality of concave sections321 face the periphery of the opening 317, the periphery of the opening317 is to be supported by the wall sections 327, and thus, stability ofthe periphery of the opening 317 can be ensured.

Since the periphery of the opening 317 and the periphery of the opening318 in the bottom plate 310 are formed in a bead shape by the concavesections 319 a and 319 c, rigidity at the periphery of the opening 317and the periphery of the opening 318 can be improved, and thus,stability at the periphery of the opening 317 and the periphery of theopening 318 can be ensured.

At a predetermined section of the cushion material 320, it is assumedthat the reference surface 320 a of the cushion material 320 is arrangedat the position vertically facing the reinforcement sections 311 of thebottom plate 310.

Thereby, when the cushion material 320 bends, the reference surface 320a can be made to sink more downward by using the difference in levelformed by the reinforcement sections 311, i.e. the turning sections 311a and the wall sections 311 b of the reinforcement sections 311.Therefore, the cushion material 320 can bend easily.

That is, not only the reference surface 310 a of the bottom plate 310and the reference surface 320 a of the cushion material 320 are tightlyin contact with each other, the reference surface 320 a partially sinkstoward the recesses of the cross-section concaved reinforcement sections311. Therefore, the cushion material 320 can be prevented from havingtrouble bending.

With respect to the bottom plate 310 and the cushion material 320, evenif the bottom plate 310 is provided with the plurality of reinforcementsections 311 and also even if the cushion material 320 is provided withthe plurality of concave sections 321, basically, the reference surfaces310 a and 320 a are in contact with each other. Therefore, the degree ofbending of the cushion material 320 is uniform overall.

As shown in FIGS. 24, 29 to 32, the cushion material 320 includes edgeconcave sections 325, 325 which are arranged near the two side edges ofthe cushion material 320, respectively, and which are to be arrangedabove the main reinforcement section 314 a of the bottom plate 310.Spaces are formed between these edge concave sections 325, 325 and themain reinforcement section 314 a.

Each of the edge concave sections 325, 325 includes ribs 325 a which areformed at a plurality of points along the front-to-back direction of thevehicle seat 301.

With such edge concave sections 325, 325, the cushion material 320 canbe made lighter. When the vehicle seat 301 is to be used as atwo-seater, since the parts corresponding to the edge concave sections325, 325 are likely to bend, sitting properties thereof, including acase where the vehicle seat 301 is used as a two-seater, can beimproved.

With respect to the plurality of ribs 325 a, the under surfaces thereofare in contact with the upper surface of the main reinforcement section314 a. Therefore, the load of a passenger who sits behind the passengerwho drives the automatic two wheeled vehicle can be supported easily.

Further, as shown in FIGS. 22 to 33, the cushion material 320 includesan abutting step section 326 which is provided around the entireperiphery edge of the cushion material 320 and which abuts the upperside of the step section 314 b of the bottom plate 310. That is, theabutting step section 326 is formed so as to correspond to the shape ofthe upper side of the step section 314 b and is tightly in contact withthe step section 314 b.

By the step section 314 b and the abutting step section 326 being incontact with each other, the entire periphery edge of the bottom plate310 and the entire periphery edge of the cushion material 320 are in aunified state. Therefore, when folding the edge 303 a of the surfacematerial 303 in to the back side of the bottom plate 310 and fixatingthe edge 303 a thereto, the surface material 303 can easily cover theedge of the bottom plate 310 and the edge of the cushion material 320.

Since a porous material such as urethane foam is used for the cushionmaterial 320 as described above, the air goes through, enters and exits,the micro pores of the cushion material 320 when the cushion materialbends and recovers from the bent state. Further, as described above, thereference surface 310 a of the bottom plate 310 where the plurality ofreinforcement sections 311 are formed and the reference surface 320 a ofthe cushion material 320 wherein the plurality of concave sections 321are formed are in contact with each other.

Therefore, one concave section 321 of the plurality of concave sections321 and another concave section 321 which is different from the oneconcave section 321 are in communication with each other through thereinforcement section 311 formed so as to be recessed at the upper sideof the bottom plate 310. Thereby, when the cushion material 320 bends,the air can be let out to another concave section 321 from the oneconcave section 321 through the reinforcement sections 311. Therefore,the cushion material 320 can bend more easily.

Since the cushion material 320 is supported by the upper surface of thebottom plate 310 and is covered with the surface material 303, there maybe a case where the air flow is blocked. In order to control this, theopening 317 is formed in the bottom plate 310 as an air passage.

According to the embodiment, since the cushion material 320 is providedwith the concave sections 321, the cushion material 320 can be madelighter even without making the cushion material 320 be thinner as in aconventional case. Thereby, while maintaining a stable sitting, thevehicle seat 301 can be made lighter. Further, since a plurality ofconcave sections 321 are formed in the cushion material 320, the cushionmaterial 320 can bend more easily.

In the embodiment, an example of a case where a plurality of concavesections 321 are formed on the underside of the cushion material 320 inorder to make the cushion material 320 bend at the part other than itsupper layer part is described above. However, as long as the cushionmaterial 320 bends at a part other than its upper layer part, a cushionmaterial of a form other than the above described form can be applied.

For example, a cushion material made of a soft foam material such asurethane foam, polypropylene foam, polyethylene foam, etc. has atendency to bend at the high density part, in general. Therefore, if thedensity at the lowest layer part of the cushion material is made to bethe densest, the cushion material can be formed so as to bend at thelowest layer part even if the concave sections 321 are not formed. Thatis, a cushion material that bends at the lowest layer part can berealized without considering its shape and the like.

With respect to the cushion material 320 having the concave sections321, if the density at the lowest layer part is made to be the densest,the cushion material 320 is more likely to bend at the lowest layer partthereof and the cushioning properties can be improved.

In the above embodiment, an example of a case where the space sectionsof the present invention are the concave sections 321 opened at thelower parts thereof is described. However, the space sections themselvesmay be closed. For example, when forming a cushion material with a softfoam material, closed space sections may be formed by forcing the air tobe injected before the soft foam material becomes solidified.

As shown in FIG. 42, the lower ends of the concave sections 321 may beclosed by attaching a laminate member 210 across the entire undersurface of the cushion material 320. The laminate member 210 is aplate-like member of resin, and air holes 211 to ensure air passage frominside the concave sections 321 are formed at the parts corresponding tothe concave sections 321.

Since the laminate member 210 is layered across the entire under surfaceof the cushion material 320, the lower parts of the concave sections 321are closed. Therefore, the air inside the concave sections 321 can bemaintained and a stable cushioning properties can be ensured.

Further, since the air holes 211 which ensures air passage from theconcave sections 321 are formed in the laminate member 210, small amountof air enters to and exits from the concave sections 321 through the airholes 211 according to bending of the cushion material 320. If theconcave sections 321 are completely closed, there is a possibility thatbending of the cushion material 320 is inhibited due to the air in theconcave sections 321. However, if small amount of air enters to andexits from the concave sections 321 through the air holes 211, thecushion material 320 can bend smoothly while stable cushioningproperties are ensured.

INDUSTRIAL APPLICABILITY

The bottom plate structure of the vehicle seat according to theembodiment can be used in a vehicle seat which is to be mounted on a twowheeled vehicle or the like, for example.

DESCRIPTION OF SYMBOLS

-   -   1 vehicle seat    -   1 a lowest position    -   2 vehicle body    -   2 a seat rail    -   3 surface material    -   3 a edge    -   4 staple    -   10 bottom plate    -   11 reinforcement section    -   11 a turning section    -   11 b wall section    -   11 c bottom    -   12 mounting section    -   12 a leg section    -   13 intersection    -   13 a reinforcement rib    -   14 rim reinforcement section    -   14 a main reinforcement section    -   14 b step section    -   14 c bent section    -   18 engaging section    -   18 a claw section    -   20 cushion material    -   21 concave section    -   22 mounting section corresponding part    -   23 expected ischium section    -   24 insertion section    -   25 edge concave section    -   26 abutting step section

The invention claimed is:
 1. A cushion material structure of a vehicleseat, comprising: a cushion material having concave sections each formedat a back side of the cushion material, wherein: the cushion material issupported by an upper surface of a bottom plate that is provided on avehicle body, wherein each concave section is opened toward the bottomplate, the bottom plate includes at least one reinforcement section thatbulges at a back side of the bottom plate and that is recessed at anupper side of the bottom plate, an under surface of the cushion materialis in contact with the bottom plate at one edge of an opening of atleast one of the concave sections and is separate from the bottom plateat an opposite edge of the opening of the at least one of the concavesections, the at least one reinforcement section is arranged so as to beopposed to at least one of the concave sections, a central concavesection that is the concave section in a width-wise center of thecushion material is in contact with a portion of the bottom plate wherethe reinforcement section is not formed, and a part of a periphery of anadjacent concave section that is the concave section adjacent to thecentral concave section is opposed to the reinforcement section, thepart being on a side near to the central concave section.
 2. A cushionmaterial structure of a vehicle seat, comprising: a cushion materialhaving concave sections each formed at a back side of the cushionmaterial, wherein: the cushion material is supported by an upper surfaceof a bottom plate that is provided on a vehicle body, wherein eachconcave section is opened toward the bottom plate, the bottom plateincludes at least one reinforcement section that bulges at a back sideof the bottom plate and that is recessed at an upper side of the bottomplate, the at least one reinforcement section is arranged such that atleast a part of the at least one reinforcement section is opposed to atleast one of the concave sections and such that the at least onereinforcement section is wider than the at least one of the concavesections, the bottom plate comprises non-reinforcement sections wherethe reinforcement section is not formed, and the at least onereinforcement section and the non-reinforcement sections are alternatelyarranged such that each of the reinforcement section and thenon-reinforcement sections is opposed to one of the concave sections. 3.A cushion material structure of a vehicle seat, comprising: a cushionmaterial having concave sections each formed at a back side of thecushion material, wherein: the cushion material is supported by an uppersurface of a bottom plate that is provided on a vehicle body, whereineach concave section is opened toward the bottom plate, the bottom plateincludes at least one reinforcement section that bulges at a back sideof the bottom plate and that is recessed at an upper side of the bottomplate, the at least one reinforcement section is arranged such that atleast a part of the at least one reinforcement section is opposed to atleast one of the concave sections and such that the at least onereinforcement section is wider than the at least one of the concavesections, and the bottom plate includes at least one opening that isopposed to the concave section of the cushion material.